The majestic and serene Alps are being gravely impacted by climate change (Fig. 1). Scientists have found temperatures to be increasing in the Alpine region, with the greatest temperature increases in cantons Geneva and Valais: Switzerland’s temperature has increased over twice the global average of 1ºC in the 20th century, with the majority of warming occurring in the 80s-00s (Rebetez and Dobbertin 2004). With increasing temperatures comes decreasing snow cover and increasing glacier reduction. In fact, the Alpine glaciers have lost about 60% of their volume since 1850, the number of annual days of snowfall at 2,000m above sea level has dropped by 20%, while the number of annual days of snowfall below 800m above sea level has dropped by 50% (MeteoSwiss 2018).

Alpine glaciers and precipitation patterns have hidden impacts of staggering magnitudes: Switzerland, France, Germany, and Italy all rely on the Alps to irrigate four major basins (the Rhine, the Rhone, the Po, and the Inn). In fact, the Alps are known as the “water towers of Europe” for the 150,000,000 people who live in these basins and depend on alpine water (Beniston 2019). Water is collected and stored as snow and ice in glaciers and glacial lakes during the winter and later released with the ice and snowmelt in the hotter months to supply neighboring basins. However, with an increase in temperatures, run-off is expected to increase in the winter and decrease in the summer, creating an imbalance in the supply-and-demand chain along the four major basins (Hill 2012).

Right in the middle of the Rhône basin valley is the capital of Valais, Sion (Fig. 2). At an elevation of 1,611 feet, Sion is not a ski-resort town but still relies on the tertiary (service) sector to feed its economy. Its main agro-economic activities include cultivation of permanent crops (orchards and vineyards) and livestock production (Fuhrer et al. 2014). Therefore, the city would be gravely economically impacted by projected inconsistent flooding and drought periods as a result of climate change. Already Sion has suffered from climate change: in 2018, Sion saw significantly warmer temperatures compared to the 1960-1991 averages. There were only seventy-three frost days (days in which the average temperature was below 0ºC) compared to the ninety-seven expected, while there were 125 summer days (days in which the average temperature was over 25ºC) compared to an expected norm of fifty-five (MeteoSwiss 2019). I created the first null hypothesis, that there is no significant temperature increase in Sion across all months. I created another null hypothesis that stated there would be no change in snow depth in winter months (November-March).

In order to analyze climate trends, I took 1955-2019 temperature, precipitation, and snowdepth data from the NOAA station located in Sion, Switzerland. While the data collection may be unreliable and lead to a warm bias due to the urban heat island effect, compounded by the tendencies of valleys to trap heat, scientists do their best to homogenize the data by comparing data in nearby areas to adjust for error. I created two sets of data for the maximum and minimum temperatures in Sion (TMAX and TMIN, respectively). Each set of data had twelve separate graphs that showed monthly TMAX and TMIN means plotted against years 1955-2019 as well as a best-fit line (Figs. 3 and 4). Figure 5 summarizes the plots of each graph: it provides slope and “R2” values and analyzes the significance for each plot. Note each best fit line has a clear positive (or increasing) slope except for February’s TMIN, suggesting overall increasing temperatures. Results are significant if there is at least one * next to the slope value; this means that the p-value is less than .05 and one can reject the null hypothesis. NS means that there is no significance.

TMIN significantly increased in April-August as well as October. TMAX increased significantly in March, April, and June-August. Because not all of the best-fit lines were statistically significant, we cannot reject the first H0 (that temperatures are rising in Sion). However, in all of the summer months (June-August), the p-value was less than 0.05–we can conclude that Sion is significantly warming in the summer months and partly reject the null hypothesis.

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To analyze precipitation and snowdepth data, I created graphs for each month of the total monthly precipitation plotted from 1955-2015. I did not use the mean of each month because there are more days that have zero precipitation or snow than not; the presence of zeroes would lower the mean and lead to insignificant results. Surprisingly, I had to accept the null hypotheses that there was a significant change in precipitation. All the graphs I generated in R were insignificant. The only statistically significant graph, as seen in Figure 6, was the precipitation for February 1955-2015, which showed an increase in inches of yearly precipitation (F-statistic=4.434, DF=59, p-value=0.0395). Moreover, there was no general slope trend: the slopes of months January, February, March, June, August, November and December were all negative while April, May, July, September, and October were all positive.

As for the snowdepth, there were no significant results for any graph. The closest a graph got to being significant was the total January snowdepth for 1955-2015 (Fig. 7), which had a p-value of .05191 and a downward-trending slope. Across monthly graphs of February, March, April, and December there were negative insignificant slopes. I accepted the second null hypothesis; there is no change in precipitation or snowdepth in winter months in Sion. There was no snow in May through September in Sion, and slight increases in October and November. Despite my insignificant precipitation and snowdepth data, multiple studies have shown that there is both an expected seasonal shift in precipitation, with higher and more intense precipitation in the winter but reduced precipitation in the summer, and an expected decrease in snowdepth overall (Gobiet et al. 2014; Hill 2012; MeteoSwiss 2018).